The present invention relates to an apparatus and method for determining the operational status of an automobile. In particular, the present invention provides a method and apparatus for protecting and maintaining the charge within a battery.
Motor vehicles, such as cars, marine vessels, trucks and the like almost universally include a battery that is used for engine ignition. The battery is also electrically connected to other electrical loads in the vehicle, such as hazard lights, radios, running lights, etc. Typically, a generator or alternator, driven by the engine, provides an electrical current for recharging the battery.
Oftentimes, the engine is shutoff and the battery continues to drive an electrical load in the vehicle and, in doing so, discharges the battery. In some cases, this can be inadvertent, such as leaving the headlights on, leaving the radio on, leaving the ignition keys in the accessory or on position, or through a malfunction in the electrical circuit. In any event and after a period of time, the battery will discharge to such an extent that engine cranking using the charge in the battery is impossible.
Accordingly, and in order to maintain a minimal threshold charge value in an automotive battery, it would be desirable to have a battery protection system which would disconnect the battery from an electrical load or draw, if the battery discharges below a set value. In addition, the system would need to distinguish the current status of the automobile (i.e. engine running) and the type of electrical systems being driven by the battery (i.e. hazard lights) in order to provide the system with a xe2x80x9cfail-safexe2x80x9d protection system so that the battery is not disconnected from driving critical systems.
Moreover, the system will also be required to determine when to reconnect the battery in order to drive such systems.
In connecting a battery to a supply of D.C. power of the same voltage rating such as a battery charger, the battery and supply must be connected with their polarities matched. If the polarities are mismatched, a high-current condition might occur. The results will be possible damage to the battery or damage to the electrical components of the vehicle.
A similar situation may occur when a motorist attempts to xe2x80x9cjump startxe2x80x9d a vehicle having a dead battery, by using jumper cables to connect the dead battery to a vehicle having a fully charged battery. It is important that the positive terminal of the first battery be connected to the positive terminal of the second battery, and likewise for the negative terminals. However, it is not always possible to guarantee correct polarity matching. In a first situation, an unsophisticated motorist may not know how to properly connect the jumper cables. In a second situation, it may be difficult to determine the polarities of the batteries. This latter situation can occur when the polarity indicating indicia on the batteries is covered with oil and dirt, at night when the indicia is difficult to read, or in the haste and frustration that arises from attempting to jump start a car during extremely adverse weather conditions. Even under ideal circumstances, errors in matching polarities can still occasionally occur due to simple oversight.
In those instances in which polarities are mismatched during an attempt to start a stranded car, not only can the error cause damage to both vehicle electrical systems, but such damage may result in both vehicles becoming disabled in a remote location. For these reasons, it is highly desirable to prevent mismatching of battery polarities when a motorist is attempting to jump-start a stranded vehicle.
Accordingly, there is a need for a battery protection system that prevents the damage to the battery from short circuits or improper jump-start conditions. In addition, there is also a need for a battery protection system wherein the battery maintains a minimal charge for operating essential systems, such as the starter motor of an automobile.
A smart battery system designed to provide crank protection includes additional features such as jump-start reverse polarity protection, short circuit protection and storage mode discharge protection.
The crank protection uses an electronic switch, i.e. FET, which opens to disconnect the battery from the vehicle electrical load to guarantee that adequate cranking energy is always available. The reconnection of the battery is transparent to the user. A re-connect occurs when the brake pedal is depressed, the hazard lights are turned on or the starter motor is turned on. If the hazard lights are activated, the battery protection system is inhibited from disconnecting the battery. If the engine is running, the battery protection system is inhibited from disconnecting the battery from the vehicle load. A manual switch is available to act as a backup.
If a dead short occurs between the battery negative and the positive terminal of the battery protective system, as may happen in a crash, the electronic switch opens, thus disconnecting the battery from the vehicle load. Additionally, if a jump-start is attempted with reverse polarity, the battery is disconnected. The short circuit and reverse polarity protection features may be part of a simpler embodiment that does not include the crank protection features.
An exemplary embodiment of the inhibit-disconnect detection comprises detection of AC signals on the vehicle electrical load that represent hazard light activation or engine running condition. The transparent detection also detects transient changes in a DC voltage across the vehicle electrical load during FET open conditions.
An exemplary embodiment of a standalone short circuit and reverse polarity system includes the electronic switch and an excessive current draw detection condition. The excessive current draw detection would not include an engine start condition that normally has a relatively high current condition.
The battery protection system includes a manual switch that allows the battery protection system to be turned off. With this switch in the off position, the battery is disconnected. With the switch in the on position, the battery protection system is enabled.